Weyand said that the Brexit deal was shaped by London, and the country's parliament should treat it as a win.
The Brexit process has grown increasingly surreal since Parliament rejected Mrs May's divorce deal two weeks ago, leaving Britain lurching towards a cliff-edge "no-deal" departure from the bloc on March 29.
Facing the prospect of another doomed vote in the British Parliament, she agreed on Tuesday to take her draft "Brexit" plan back to Brussels to try and get the Europeans to accept changes to a key provision on the Irish border.
"We have to have a deal which can carry the support of parliament and that's going to require some changes to the withdrawal agreement", May's spokesman said, as Downing Street tried to seize the initiative back from MPs.
Theresa May had urged MPs to vote in favour of it to give her a mandate to return to Brussels and re-open negotiations in order to secure a "legally binding change".
May's approach drew praise from Brexit-backing lawmakers but prompted scorn from their pro-EU colleagues. "But if she really wants to reopen the whole thing, then it's a "No".
Growing expectations that Britain can avoid a no-deal Brexit have fuelled a 3 percent rally in the pound this month against the dollar and the euro.
There have been warnings that borders will be snarled up, hitting trade and leading to shortages.
"If the Brady amendment goes through now sterling will fall even more", he added.
The amendment backed by the prime minister calls for the backstop to be replaced with "alternative arrangements to avoid a hard border".
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If voters are told that Medicare for All requires raising taxes and long wait times at the doctor, support for it collapses. He's booked for Thursday as part of a "Dignity of Work" tour that he plans to begin on Wednesday in his home state.
May wants lawmakers to support the proposal or amendment authored by senior Conservative lawmaker Graham Brady to call for the backstop to be removed and replaced with "alternative arrangements" during a series of votes, which are due to start at 2 p.m. ET.
The proposal - put forward by Tory MP Sir Graham Brady - had the support of the government and won by 16 votes.
An official in Brussels said such a proposal would not work for the European Union, but it is not a foregone conclusion that lawmakers will back it, one of seven proposed to try to break the impasse.
One amendment would open the door for the House of Commons to bring in legislation preventing Britain leaving the European Union without a deal by forcing May to delay Brexit for nine months if her deal is not approved before February 26.
She said the government will come back to make a statement to Parliament on the next steps if no Brexit deal has been agreed by February 13.
Britain is reportedly making plans to declare a "state of emergency" and introduce martial law in the event of disorder breaking out following a No Deal Brexit.
British MPs seeking to pressure Prime Minister Theresa May this week to renegotiate her Brexit deal should heed European Union warnings that it will not succeed, Ireland's foreign minister warned on Sunday.
"In the absence of a viable alternative to the Withdrawal Agreement, we continue to be heading for a no-deal scenario which is damaging, disruptive and chaotic to business, to manufacturers and consumers", Sanguinetti said.
Some Brexit-backing Conservative lawmakers, who voted against May earlier this month, have indicated they would support her divorce deal "subject to this change".
A statement from the Irish government said the withdrawal agreement is "a carefully negotiated compromise, which balances the United Kingdom position on customs and the single market with avoiding a hard border and protecting the integrity of the EU customs union and single market".